This invention relates generally to water heaters for heating potable water and more particularly to a water heater that does not require a series of heat exchanger tubes.
In known water heaters such as described in U.S. Pat. Nos. 4,651,714 and 4,875,465, a tubular member serving as a combustion chamber is mounted in an opening in the side of a water tank and extends horizontally across the lower portion of the tank. An elongated burner is positioned within the combustion chamber. The waste gases of combustion generated by igniting a fuel-air mixture are discharged from the inner end of the tubular member and are directed into a series of heat exchanger tubes, which are positioned beneath the combustion chamber. The outer ends of the heat exchanger tubes extend through the wall of the tank and communicate with a flue collector through which the waste gases can be discharged.
Because the above-mentioned water heaters require a relatively large number of components, and further because of the particular type of construction such systems require, these water heaters are vulnerable to failure in several different ways. For example, the narrow heat exchanger tubes may fail as a result of corrosion through exposure to water in the tank, exposure to combustion gases in the tubes themselves, or through simple metal fatigue. Tube joints may also fail where the tubes are attached to the tube sheet. Thus, even a small water heater that has only a few heat exchanger tubes may fail in one of a multiple of different ways.
When such failures do occur they are difficult to correct. The process of replacing a heat exchanger tube is costly and time consuming, requiring that the heater be shut down and drained so that the entire chamber can be removed. An alternative procedure requires that the defective heat exchanger tube be sealed off so that the waste gases do not flow therethrough. However, this alternative method is not satisfactory because it increases the time required by the water heater to heat the water and, additionally, it is often a violation of local boiler codes. Furthermore, only a small number of heat exchanger tubes in any given water heater may be sealed off before the heater fails to operate properly.
An additional problem with these known water heaters is that it is expensive and time consuming to construct the heat exchanger tubes and mount them individually in the chamber. Furthermore, as the input power of the water heater increases, the number of heat exchanger tubes that are required increases and hence the time and expense also increases.